This invention relates to high speed wire matrix print heads, which accurately locate the armatures of the print head with respect to the print pins and magnetic yokes, and the establishment of a predetermined spring load along a fulcrum point contact line between the magnetic yoke, the armature and its guide and supporting springs. Gap adjustments are also provided in the form of two or four adjustment screws for achieving precise gap adjustment which compensates for any mechanical tolerance buildups in the device.
The present invention in general relates to wire matrix print head assemblies of the type shown in U.S. Pat. Nos. 4,230,038 and 4,230,412. In this type of matrix print head a plurality of print pins are spaced about a central axis and are longitudinally movable thereabout between a print and a non-print position. A plurality of guide means in the form of an armature housing or nose are provided for guidably supporting the print wires or pins and a plurality of armature members which are circumferentially spaced in the armature housing and extend radially outward from the central axis. The armature members have an inner portion engageable with one of the print pins for driving the print pin when actuated on the outer end thereof by a plurality of electromagnetic means each having a magnetic yoke mounted adjacent to the outer portions of the armature for causing pivotal movement of the armature with the outer portion moving toward the electromagnetic means when a magnetic force is applied thereto and the inner portion of the armature striking its associated print pin. In the aforesaid patents the armatures are positioned in a housing which permits free sliding movement therein with the magnetic members being mounted on a one piece housing utilizing a threaded fastening means which can be adjusted to vary the axial air gap between the various magnetic yokes and their associated armatures as well as adjusting the armature movement. In the U.S. Pat. No. 4,230,412 patent the armatures are mounted for free sliding movement in the armature housing and the armatures are pivotally supported on the radially innermost magnetic yoke portions with a resilient O-ring located opposite each yoke which continuously engages the armature and is held in such a position by the armature housing.